Fuel injection pump for internal combustion engines

ABSTRACT

A fuel injection pump for internal combustion engines has a fuel-quantity adjusting member, and an adjusting device associated with the adjusting member and operative for altering a possible travel of the fuel-quantity adjusting member as a function of an atmospheric pressure. The device has a pivotally mounted two-armed stop lever against which the fuel-quantity adjusting member can be brought to rest. A circuit is provided with a working element which acts on the stop lever and changes its position or length following a closure and opening of the circuit. The adjusting device has a switching element which is acted upon by the atmospheric pressure and, as a function of atmospheric pressure closes and opens the circuit.

BACKGROUND OF THE INVENTION

The invention relates a fuel injection pump for internal combustionengines. More particularly, the present invention relates to a fuelinjection pump for internal combustion engines which has a fuel-quantityadjusting member and an associated adjusting device for altering thepossible travel of the fuel-quantity adjusting member as a function ofthe atmospheric pressure.

Such a fuel injection pump has already been disclosed in GermanOffenlegungsschrift 3,430,141. This fuel injection pump has a stop leverwhich is adjustable via a transmission device by a pneumatic actuator asa function of the atmospheric pressure and against which a speed leverof the fuel injection pump. The speed lever serves as a fuel-quantityadjusting member, comes to rest at full load. The pneumatic actuatorhere comprises two diaphragm cells which are connected in series andchange in length as a function of the atmospheric pressure. This changein length is transmitted to the stop lever via the transmission device,which has two discs coupled to one another in such a way that they canbe dragged along. Assigned to the transmission device is a lockingmechanism which locks the said device counter to the action of the forceof the stop lever. The overall arrangement with the pneumatic actuator,the transmission device and the locking mechanism thus comprises a largenumber of individual parts and is expensive to manufacture and assemble.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a fuelinjection pump for internal combustion engines which avoids thedisadvantages of the prior art.

In keeping with theses objects and with others which will becomeapparent hereinafter, one feature of the present invention resides,briefly stated in a fuel injection pump of the above mentioned generaltype in that the adjusting device has a switching element which is actedupon by atmospheric pressure and, as a function of the atmosphericpressure, closes and opens a circuit into which a working element actingon a stop lever is connected, and the working element changes itsposition or its length following the closure and opening of the circuit.

The fuel injection pump for an internal combustion engine designed inaccordance with the present invention has the advantage that the stoplever is adjustable by simple means as a function of the atmosphericpressure.

In accordance with a further feature of the present invention theswitching element is designed as an electrical switch, the circuit isdesigned as an electric circuit and the switching element closes thecircuit when a certain value of the atmospheric pressure is undershot.

The working element in accordance with the present invention can beelectrically heatable and can change in length as a function oftemperature.

In accordance with still another feature of the present invention theworking element is designed as an element based on an expandingmaterial. With this feature the adjustment of the stop lever is limitedto a predetermined value.

Further, the adjustment of the stop lever brought about by the workingelement can be limited by a counterstop.

The counterstop can be adjustable. On its side opposite to the stoplever, the working element can be supported via a spring. By virtue ofthe support of the working element, the working element can expandtoward the spring when the stop lever is resting against thecounterstop.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specific embodimentwhen read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure shows a fuel injection pump in the form of a longitudinalsection.

DESCRIPTION OF A PREFERRED EMBODIMENT

A distributor-type fuel injection pump has a pump plunger 12 whichoperates in a cylinder bore 11 of a casing 10. A reciprocating and,simultaneously, a rotary motion are imparted to the plunger via a driveshaft 34 by a cam drive comprising a roller ring 13 and a front-face camdisc 14. During the suction stroke of the pump plunger 12, a pumpworking space 15 formed by the pump plunger 12 in the cylinder bore 11is filled via a suction bore 16 and control grooves 17 in the pumpplunger 12. During the delivery stroke of the pump plunger 12, with thesuction bore 16 closed, the fuel is pumped via a longitudinal bore 18and a distributor groove 19 connected to the latter, via a deliveryvalve 21 and a delivery line 22, to an injection nozzle (not shown) on acylinder of the internal combustion engine operated using the fuelinjection pump. The end of delivery is reached when a transverse bore 23provided in the pump plunger 12 and connected to the longitudinal bore18, is opened by an axially displaceable control slide 24 and the pumpworking space is relieved to an interior space 25. The fuel fed into thepump working space 15 via the suction bore 16 is removed from theinjection-pump interior space 25. The space 23 serves as an inletchamber, and the fuel released from the transverse bore 23 by thecontrol slide 24 can also flow back into it. Fuel is fed to the interiorspace 25 from a reservoir by a feed pump (not shown).

A fuel-quantity adjusting device has a centrifugal speed governor 32. Arotary motion is imparted to the governor by the drive shaft 34 in amanner not shown in greater detail. Via a governor sleeve 35 and a speedlever 36, the governor actuates the control slide 24. Also acting on thespeed lever 36 is a governing spring 39, which is articulated on aspeed-adjusting lever 40 connected to the accelerator pedal. In thisrole, the speed lever 36 can be denoted as a fuel-quantity adjustingmember. The axial position of the control slide 24 set by the speedlever 36 determines the end of delivery and hence the quantity injectedby the fuel injection pump. In the illustrated full-load position of thespeed lever 36, this lever rests against a stop lever 41.

The stop lever 41 is of two-armed design and is pivotably mounted on astud 43. An adjusting device has a working element 44 which is insertedinto a bush 45 screwed into the casing 10. It is designed as atransmitter based on an expanding material, rests with one side of acollar 46 in the bush 45, and a pin 42 projects through the bush 45 intothe interior space 25 towards the stop lever 41. The working element 44is pressed towards the stop lever 41 by a spring 47 which is supportedagainst a cap part 48 inserted into the bush 45 and engages on theworking element 44 on the other side of the collar 46. The bush 45 andthe cap part 48 are fixed on the casing 10 and the bush 45,respectively, by means of a lock nut. By means of the bush 45, it ispossible to set the position of the working element 44. Screwed into thecasing 10 on that side of the stop lever 41 which is opposite to the pin42 is a screw which serves as a counterstop 49 and is fixed on thecasing 10 by means of a lock nut 50. The working element 44 is connectedinto an electric circuit 52, which is closed and opened by a switchingelement 53, acted upon by the atmospheric pressure, as a function of theatmospheric pressure. The switching element 53 is designed as analtitude switch with a diaphragm cell 54 which closes a contact in theswitching element 53 upon expansion. When the atmospheric pressurechanging with the altitude at which the motor-vehicle internalcombustion engine supplied with the fuel injection pump is driven orchanging due to some other cause undershoots a value determined by thedesign of the diaphragm cell 54, the diaphragm cell 54 closes thecircuit 52 and the working element 44 is heated. As the temperatureincreases, the working element 44 expands and, via its pin 42, pivotsthe stop lever 41 in the direction of a decreasing fuel injectionquantity. In order to limit the pivoting of the stop lever 41, thelatter comes to rest against the counter stop 49 after a certain amountof pivoting. Any further expansion of the working element 44 which thenoccurs is possible towards the cap part 48, counter to the spring 47.When the switching element 53 opens the circuit 52 again due to anincrease in the atmospheric pressure, the length of the working element44 decreases due to cooling and the stop lever 41 is adjusted in thedirection of an increasing fuel injection quantity.

The circuit 52 can also be designed as a pneumatic or hydraulic circuit.It is also possible for the switching element 53 to open and close avalve connected into the circuit 52. A working element 44 designed as apiston thereby is adjusted as a function of the pressure prevailing inthe circuit 52. Finally, it is also possible to use a working elementformed as an actuating magnet electrically controlled via the circuit.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in afuel injection pump for internal combustion engines, it is not intendedo be limited to the details shown, since various modifications andstructural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letter Patent isset forth in the appended claims.
 1. A fuel injection pump for internalcombustion engines, comprising a fuel-quantity adjusting member; anadjusting device associated with said adjusting member and a operativefor altering a possible travel of said fuel-quantity adjusting member asa function of an atmospheric pressure, said adjusting device having apivotally mounted two-armed stop lever against which said fuel-quantityadjusting member can be brought to rest, an electrical circuit, aworking element which acts on said stop lever, and a switching elementprovided in said electrical circuit and in dependence upon theatmospheric pressure controlling said working element, said switch beingactuated in response to exceeding a predetermined atmospheric pressureand opening and closing said electrical circuit, said working elementbeing connected in said electrical circuit, and said two-armed stoplever being movable by said working element when said electrical circuitis closed due to a current flow from a first position to a secondposition which is defined by abutment of said stop lever against acounterstop.
 2. A fuel injection pump as defined in claim 1, whereinsaid working element is composed of expanding material and changes itslength as a function of temperature.
 3. A fuel injection pump as definedin claim 1, wherein said counterstop is adjustable.
 4. A fuel injectionpump as defined in claim 3; and further comprising means for adjustingsaid counterstop.
 5. A fuel injection pump as defined in claim 1; andfurther comprising a spring arranged so that said working element issupported by said spring at a side which is opposite to said stop lever.